This invention relates to improvements in the manufacture of multi-ply fibrous web structure, particularly of the soft absorbent type such as, for example, paper towels.
In the manufacture of paper towels, efforts have been directed to improving important product qualities such as softness, water absorbency, and bulk. Softness, absorbency, and a degree of bulk have been imparted to multi-ply fibrous sheet structure by providing highly repetitive patterns of closely spaced embossments in confronting joined plies, in combination with application to the joined plies of decorative, relatively widely spaced spot embossments. Such a structure is disclosed and claimed in my U.S. Pat. No. 4,326,002, issued Apr. 20, 1982, from application Ser. No. 149,912, filed May 15, 1980, which was a continuation of copending U.S. patent application entitled "Multi-Ply Fibrous Sheet Structure and Its Manufacture", Ser. No. 21,915, filed Mar. 19, 1979, now abandoned, and assigned to the assignee of the present invention.
The following U.S. patents also are representative of the prior art, and are believed material to the examination of the present invention.
U.S. Pat. No. 2,854,336, in FIG. 19 thereof, discloses an embossing roll 24 having primary and secondary design protuberances 25 and 26, respectively.
U.S. Pat. No. 3,867,225 discloses a two-ply web T (FIGS. 3 and 4) wherein embossments 25 of one ply 29 are of lesser depth than embossments 17 of the other ply 30. Embossments 17 are adherent to ply 29 to hold plies 29 and 30 together.
U.S. Pat. No. 3,868,205, in FIG. 16 thereof, discloses a two-ply web wherein each of the webs have relatively deep embossments within which are formed relatively shallow, adherent embossments.
U.S. Pat. No. 3,708,366, in FIG. 2 thereof, discloses a pair of webs 6 and 7 adherent in the regions of relatively deep embossments in web 6, and non-adherent in the regions of relatively shallow embossments in web 7.
The hereinabove described U.S. patents have in common the concept of "double-depth" embossing to produce increased bulk in a two-ply web.
It is an objective of my invention to provide an improved multi-ply fibrous web structure embodying a novel and useful arrangement of double-depth embossments.
It is a further objective of my invention to provide an improved multi-ply household tissue structure embodying an arrangement of double-depth embossments that enhance its softness, water retention, bulk, and aesthetics.